// 什么是NaN?
// console.log(Number(1)); //1
// console.log(Number(null)); //0
// console.log(Number([])); //0
// console.log(Number('123')); //123
// console.log(Number(undefined)); //NaN
// console.log(Number('hello world')); //NaN
// console.log(Number({})); //NaN

// isNaN
// isNaN('123') //false
// isNaN(null) //false
// isNaN(true) //false
// isNaN([]) //false

// isNaN('hello') //true
// isNaN(undefined) //true
// isNaN(NaN) //true
// isNaN({}) //true
// console.log(isNaN("")); //false
// console.log(isNaN("   ")); //false
// console.log(isNaN(new Date())); //false
// console.log(isNaN(new Date().toString())); //true


console.log(Number.isNaN('123')) //false
console.log(Number.isNaN(null)) //false

console.log(Number.isNaN(1 / 0)) //false
console.log(Number.isNaN(undefined)) //false
console.log(Number.isNaN('hello')) //false
console.log(Number.isNaN([])) //false
console.log(Number.isNaN(0 / 0))
